The present invention relates to an apparatus and method for high speed subsurface inspection of built infrastructure. Presently, a large proportion of transportation civil infrastructure is approaching or exceeding its original design service life (as many United States interstate highways were built in the 1950s with a fifty year design life). In addition, building infrastructure can often become deficient and/or structurally challenged as structure needs evolve, aging processes occur, and material deterioration progresses. Current state of the practice methods (such as visual inspection) are extremely difficult, time-consuming, and expensive. They are inadequate for tasks including evaluating highways, bridges, and other civil structures. These state of the practice methods are inconsistent and do not quantify issues and requirements for optimum repair, rehabilitation, or replacement decisions by civil infrastructure asset owners. Many civil structures are made of poured concrete reinforced with rebar and other concrete and steel configurations (such as post-tensioned/prestressed concrete). Steel reinforcement is often embedded within the concrete, where corrosion related deterioration is a common occurrence in many parts of the world. Steel corrosion products occupy more volume than the original steel. Therefore, corrosion increases internal material stress (which frequently leads to concrete cracking and concrete delaminations). Subsurface evaluation of civil infrastructure component condition (such as a bridge deck) and detection of subsurface deterioration at an early stage can inform and encourage maintenance, rehabilitation, or replacement decisions. Skyscrapers are designed to flex to at least a small degree to accommodate to wind, heat fluctuations, and other ambient conditions. Upon construction, Quality Control/Quality Assurance (QC/QA) parameters such as concrete cover depth (from the concrete surface to the depth of the top mat of steel reinforcement can be evaluated to predict corrosion processes (where oxygen and chlorides must diffuse down to the level of steel reinforcement). Design of buildings and other structures to accommodate to ambient conditions requires complete and accurate inspection of those structures to ensure that they remain safe for use. The same is equally true of roadways and bridges which are typically configured with reinforcement or prestressed steel strands within ducts or other structures allowing them to flex, twist, expand, and contract in a reversible fashion to accommodate to ambient conditions and leading to ensure long useful life.
Over the years, several techniques have evolved to facilitate inspection of structures, buildings, roadways, and bridges. Among those techniques, most pertinent to the teachings of the present invention is the use of ground penetrating radar technology, a technology that permits inspection of structures, roadways, and bridges to determine whether reinforcing aspects embedded beneath the surface are corroded, causing material cracking or delamination cracking due to internal stresses, in need of replacement, or otherwise of concern.
While use of ground penetrating radar is an effective way to perform non-invasive inspections, in currently used ground penetrating radar inspection systems, their major impediments are that they are time-consuming and expensive to apply. To date, no one has developed a ground penetrating radar-based inspection system that can efficiently and accurately perform such inspections at high speed in a close coupled configuration. For example, on roadways and bridges, present day close coupled or ground coupled ground penetrating radar-based systems can only move at a speed below 10 mph while performing accurate evaluations, thereby causing such inspections to be extremely time-consuming. Moreover, at such speeds, the inspection vehicle bearing the inspection system impedes traffic as it works. An inspection vehicle traveling at less than 10 mph takes up an entire lane of traffic or more and will back up traffic for miles under circumstances when inspections are being undertaken during peak use times.
As such, a need has developed for a ground penetrating radar-based inspection system which can perform inspections in such a way as to not impede traffic during the process. Ideally, a system that could move at typical highway speeds or even at higher speeds would be a significant enhancement since inspections could be conducted efficiently, less expensively, and without in any way impeding traffic. It is with these goals in mind that the present invention was developed.
Applicant is aware of the following prior art:
U.S. Pat. No. 5,680,048 to Wollny teaches a handheld device using ground penetrating radar to detect metallic objects that are beneath the ground surface. Wollny fails to teach a device that is able to move quite rapidly to inspect roadways, bridges, structures, and other infrastructure.
U.S. Pat. No. 5,835,053 to Davis discloses a roadway ground penetrating radar system to generate a continuous profile of pavement structure. Davis fails to disclose the spacing between the ground penetrating radar transmitter and the roadway in question nor does Davis teach or suggest the speed of movement of the system with respect to the roadway in question.
U.S. Pat. No. 5,835,054 to Warhus et al. discloses an ultra wideband ground penetrating radar imaging of heterogeneous solids. Warhus et al. fail to teach or suggest spacing between the radar transmitter and the structure being examined nor do they teach or suggest high speed examination of such structures nor any speed of inspection for that matter.
U.S. Pat. No. 6,388,629 to Albats, Jr. et al. discloses a rotating scanning antenna apparatus and method for locating buried objects. The Albats, Jr. et al. device teaches rotation of a sensor as opposed to linear movement thereof. The patent also does not teach or suggest any speed of propagation along an object being examined.
U.S. Pat. No. 6,496,137 to Johansson teaches a ground penetrating radar array and timing circuit. This patent teaches the use of ground penetrating radar and includes a housing on wheels allowing the system to be moved. However, this patent does not teach or suggest any speed of movement thereof nor is there any teaching or suggestion of a desired spacing between the transmitter and the surface being examined.
U.S. Pat. No. 8,174,429 to Steinway et al. discloses a mine detection device. The device includes use of ground penetrating radar to detect subsurface objects. However, the only disclosure of speed of movement describes one implementation as moving the search device between 1 to 3.6 feet per second across a 5 foot lane. This is extremely slow operation indeed.